The light-emitting diode (LED) based microdisplay technology can meet the stringent demands for future augmented reality applications by providing the needed brightness, contrast, resolution, power efficiency, and device lifetime beyond the capabilities of current liquid crystal or organic LED display technologies. Because LEDs are inherently monochromatic while displays require individually addressable red, green, and blue channels, attempts to realize an LED microdisplay typically involve assembly of three types of LED devices or selective deposition of different phosphor materials on a single-color LED pixel array. Recently, various approaches have been introduced to enable monolithic integration of multi-color LED pixels on the same chip, which can potentially enable a higher spatial resolution and cut down the production cost. These methods include controlling and varying indium composition using selective area epitaxy, selective carrier injection into multiple quantum wells (MQWs) of different indium compositions, and generating and controlling colors using local strain engineering. Despite the initial successes of these monolithic approaches, color mixing has not been demonstrated. Color mixing is one of the key elements for any display technology. It requires independent and linear control of the intensity from each color channel. At the same time, the color coordinates of these color channels must remain stable. In this disclosure, we present color mixing from a full-color LED pixel comprising of three independent color channels, monolithically integrated on the same chip using local strain engineering.
This section provides background information related to the present disclosure which is not necessarily prior art.